During the past several years, the popularity and viability of fuel cells for producing both large and small amounts of electricity has increased significantly. Fuel cells conduct an electrochemical reaction with reactants such as hydrogen and oxygen to produce electricity and heat. Fuel cells are similar to batteries except that fuel cells can be “recharged” while providing power. In addition, fuel cells are cleaner than other sources of power, such as devices that combust hydrocarbons. Fuel cells provide a direct current (DC) voltage that may be used to power almost any electrical device such as, motors, lights, computers, or any number of electrical appliances.
Fuel cells typically have three component parts: an anode, a cathode, and an electrolyte. The electrolyte is sandwiched between the anode and cathode. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified, depending on the type of electrolyte used, into one of five groups: alkaline fuel cells (AFC), phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), and proton exchange membrane fuel cells (PEMFC). One variant of the PEMFC technology includes direct methanol fuel cells (DMFC), in which liquid methanol is directly fed to the fuel cell as fuel.
PEMFCs typically function by supplying hydrogen to the anode. The hydrogen is used by the anode to provide protons to the electrolyte and releases electrons that pass through an external circuit to reach a cathode located opposite the anode. The protons solvate with water molecules and diffuse through the membrane to the cathode where they react with oxygen that has picked up electrons thereby forming water. PEMFCs have a number of distinct advantages over other fuel cells. PEMFCs have a very high power density (40% to 60% efficiency) and a very low operating temperature (around 80 degrees Celsius). Moreover PEMFCs do not utilize dangerous chemicals that may spill or leak. These qualities make PEMFCs extremely safe and low in maintenance requirements.
Traditionally, the proton exchange membrane (PEM) of a PEMFC has been formed by applying a solid semipermiable membrane to an electrode layer with an adhesive layer between the two. The membrane-adhesion layer electrode stack would then be compressed in the presence of heat to bond the layers together. However, traditional methods of forming PEM fuel cells tend to have a low amount of mechanical stability and are susceptible to swelling of the electrolyte. This swelling of the electrolyte often leads to increased fuel crossover resulting in degraded fuel efficiency of the fuel cell.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.